If you want to without buying it, go onto coolrom.com, go under Emulators, Nintendo 64, download project 64. Then go under ROM files, nintendo 64. Ocarina of Time and Majora's Mask are right beside each other on the Top 50 rated. Download them both and get to playing.

P.S. If you have an Xbox 360 controller you can use it as a controller for the Emulator.
P.S.S. If you have any problems, feel free to ask.